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November 4, 2008 | 12 Comments

TV…no, wait…rain causes autism

A few months ago we looked at a paper that purported to show that watching TV causes autism. Well, that paper has finally been peer reviewed, and therefore published. It’s making the rounds in the media on this historically slow news day.

Monthly Weather Review chief editor Dave Schultz found this article on the BBC web site. Climate-computer guy Dan Hughes found another at the Washington Post.

The original draft paper is here. If you are in one of the ivory towers, you can download the paper here, at the Archives of Pediatrics & Adolescent Medicine.

The idea is that when it rains it drives kids inside to watch television and that watching TV—never mind how—induces autism. The more hours kids spend in front of the boob-tube, the more cases of autism. Since you can’t measure the number of hours of watching TV, you have to do something else. The authors decided that precipitation would be a good proxy. Here are some of the comments from July:

But how can you tell how much TV all these kids watched? You can’t. There is no way to go back to 1970 and count how many hours each baby watched TV. This is a dilemma, because we would really like to test the dose-response. Perhaps there is a proxy? A proxy is a stand-in variable that is so strongly associated with hours of TV watched that it’s almost as good as the real thing. Can you think of any?

How about precipitation? Sure, rain and snow. After all, when it rains, what else is there to do but watch TV? Actually, lots, and when it snows, there’s even more. But, this is the proxy chosen by the researchers (their Figure 6 will hold some interest for those interested in global warming).

They plotted up maps by county for California, Oregon, and Washington, and colored in counties that had more than median precipitation (from 1990-2001) and then colored those with higher than median autism rates. These colored squares tended to be in the same spot, and is what led them to the conclusion that watching TV causes autism. Case closed.

Mark Lever, chief executive of The National Autistic Society, is properly sanguine about the research. He said, “the latest theory would join a succession of others advanced about the condition and its origins.”

In recent years autism has been linked to factors as varied as older aged fathers, early television viewing, vaccines, food allergies, heavy metal poisoning, and wireless technology, to name just a few.

Some of these theories are little more than conjecture or have been discredited, others seem more promising and are in need of further study. As yet, however, very few have been substantiated by scientific research.

We don’t yet understand what causes autism, although scientists do believe that genetic factors might play a part.

People with autism and their families are naturally concerned to get the right information and there is a lot of confusion and concern over the conflicting theories put forward.

Another guy named Weiss “thinks the results of the study need to be taken with a grain of salt.” To counter that, a man called Lathe said, “Emissions from manufacturing industries, power plants, and from domestic waste incineration generally rise to the troposphere to be diluted into the large volume of the atmosphere. Precipitation can dump this load back on the land, to be absorbed by plants and animals in the food chain.” Not very good meteorology there, because we could equally say that lack of precipitation allows the atmospheric pollution to be worse, causing increases in inhaled ozone, etc. etc.

Overall, there doesn’t seem to be a solid link between rain or TV and autism. The authors of the paper even say “that families more prone to having autistic children may reside in areas with high levels of precipitation, or that such areas might use broader diagnostic criteria for diagnosing autism.” There does seem to have been an increase in the rates of autism, but that increase could very easily be from increased awareness and subsequent diagnoses of the disease.

Nothing has changed between the draft work and the peer-reviewed one to cause me to change my mind about the value of the paper. What I didn’t know before, but I learned from the Post today, is that the lead author and economist Waldman has a son who is autistic. I can therefore understand what motivates him and the desire to find out what happened.

November 3, 2008 | 11 Comments

“Beware of geeks bearing formulas”

Those are the words of Warren Buffet, who warned of the coming credit crisis. Buffet—one of the very few—had little faith in the “complicated, computer-drive models systems that many financial giants relay on to minimize risk.”

Reader Dan Hughes reminds us of this article in today’s Wall Street Journal, which looks at why AIG did so miserably.

AIG built a lot of models which attempted to quantify risk and uncertainty in their financial instruments. They, like many other firms, tried to verify how well these models did, but they only did so on the very data that was used to build the models.

Now, if you are a regular reader of this blog, you will know that we often talk about how easy it is to build a model to fit any set of data. In fact, with today’s computing power, doing so is only a matter of investing a small amount of time.

But while a model fitting the data that was used to build it is necessary condition for that model to work in reality, it is not a sufficient condition. Any model must also be tried on data that was not used—in any way—to build it.

What happened at AIG, and at other financial houses, was that events occurred which were not anticipated or that had not happened before. Meaning, in short, that the models in which so many had so much faith, did not work in reality.

There is only one true measure of a model’s value: whether or not it works. That it is theoretically sound, or that it uses pleasantly arcane and inaccessible mathematics, or that it matches our desires, or that “only PhDs can understand” it are all very nice things, but they are none of them necessary. Many complex models which are in use are loved and trusted because of these things, but they should not be. They should only be valued to the extent that they accurately quantify the uncertainty of the real-life stuff that happens (climate models anyone?).

What the AIG models failed to account for were the “unknown unknowns”—to use Donald Rumsfeld’s much maligned quotation. They did not quantify the uncertainty of events which they did not know about. They thought that the models quantified the uncertainty of every possible thing that would happen, but of course they did not. Meaning that they were overconfident.

AIG’s failure is yet another in a long series of lessons that the more complex the situation, the less certain we should be.

(A subscription is required to read the full WSJ article.)

November 2, 2008 | No comments

Signed copies: update

I’ll be placing the order for the books tomorrow (Monday) morning. I’ll order a few more in case anybody else orders a signed copy. I imagine I’ll have the books by the end of the week, at which time I’ll mail them out. Look for updates here. Naturally, everybody who ordered will get an email.

Thanks for your support everybody!

October 31, 2008 | 15 Comments

Breaking the Law of Averages: Real-Life Probability and Statistics in Plain English

It is finally done!

Breaking the Law of Averages

You may order directly from the publisher here1. The book will also be available on Amazon, Barnes and Noble, etc. in about a month. I’ll update this post with the links when the book is in the distribution channels. Order as many copies as humanely possible.

Signed copies
I have had several requests for signed copies. I’ll be happy to do this for people. If you want a signed book, please email me at matt@wmbriggs.com. Please use “SIGNED COPY” as a subject line, and include your address in the body of the email. I’ll buy a few books from the publisher and then re-ship them out to people who want a copy. The charge will be the same as the publisher’s plus the same as they charge for Media Mail shipping and handling ($5.90), plus $1.15 cents (to cover tax). This makes the cost an even US$32.00. Payment will be arranged through PayPal (apparently, you don’t have to have an account to pay this way). I’ll send those who email me a PayPal “Request for Payment”; after that is received, I’ll ship the book (anywhere in the world).

Because I first have to order copies, sign them and then mail them out, it will of course take longer for you to get your book. I will wait a couple of days to see how many people email so I have a rough idea of how many books I should order.

I have two permanent places for news of the book:

  1. My books tab (see upper right of screen): general news and information
  2. Code page: free R code examples, erratum, links to papers, data, etc.

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Why is this book different?

Statistics has traditionally been taught decade after decade in a fashion that is long outdated. This book presents a brand new way of understanding probability and statistics at the introductory level. The approach taken does not require mindless memorization. There is very little math, and what there is requires nothing beyond multiplication and division. This book takes busy work out of standard statistics and puts insight back in.

Preface excerpt:

The regular readers of my blog, where parts of this book previewed piece by piece, provided razor sharp editing and keen questioning and kept me from making major blunders. So thanks to (screen names) Mike D, JH, Harvey, Joy, Noahpoah, Harry G, Bernie, Lucia, Luis Dias, Noblesse Oblige, Charlie (Colorado), Dan Hughes, Mr C Physics, Jinnah Mohammed, Ari, Steve Hempell, Wade Michaels, Raphael, TCO, Sylvain, Schnoerkelmanon, and many others (sorry if I left you out!). Any mistakes left are obviously their fault.

What’s next?
I use the book in my own classes, of course, and a few other professors have been either using a draft or have expressed interest in the book for their classes. If, by some miracle, the book becomes popular, I’ll start working on a “Answers to Selected Exercises” or, given that I get substantial comments from actual class use, a Second Edition. But that is all in the far, far future.

If you are a professor of a statistics class and want to chat about the book, send me an email at matt@wmbriggs.com and we can set up a time to talk. I have had great success with this approach for beginning students and can let you know how I run the class. Some guidelines are also given in the Preface.

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1The cover art looks terrible on the publisher’s page. They have scaled it down from an enormous PDF to a small JPEG and it is pixelated. It looks great when printed, however.